稀土Ce对7A04铝合金耐腐蚀性能的影响

目的提高7A04铝合金的耐腐蚀性能。方法采用周期浸润腐蚀试验模拟海洋大气环境,研究了不同稀土Ce含量的7A04铝合金的腐蚀行为及规律。通过金相显微镜和扫描电子显微镜,观察了不同试样的组织和夹杂物形貌。采用失重法和电化学阻抗技术,分析了试样的腐蚀动力学规律及电化学行为特性。结果在Ce质量分数分别为0%、0.39%和0.81%的7A04铝合金中,稀土Ce的加入量为0.39%时,其晶粒最细小,第二相与夹杂最少且分布最均匀,合金的基体组织得到了改善。稀土7A04铝合金的腐蚀失重明显低于不含稀土Ce的7A04铝合金,且锈层电阻升高,其中含0.39%稀土Ce的7A04铝合金的锈层电阻最高。结论三种7A04铝合金均发生了明显的局部腐蚀,主要为点蚀。稀土Ce的加入,改变了非稀土铝合金中的T相和S相,生成了新的细小的块状金属间化合物,改善了组织的均匀性,提高了其腐蚀锈层电阻,增加了锈层对基体的保护能力,使铝合金耐海洋大气腐蚀性能提高。在三种稀土Ce含量的铝合金中,含0.39%稀土Ce的7A04铝合金的耐蚀性最佳。

Effect of Rare Earth Ce on Corrosion Resistance of 7A04 Aluminum Alloy

The work aims to improve corrosion resistance of 7A04 aluminum alloy. Corrosion behavior and rule of 7A04 with different contents of rare earth Ce by simulating marine atmospheric environment with alternate immersion test. Microstructure and inclusion morphology of different samples were observed by using metallographic microscope and scanning electron microscope (SEM). Corrosion dynamic law and electrochemical behavior characteristics of the samples were analyzed in the method of weight loss and electrochemical impedance spectroscopy (EIS), respectively. In the 7A04 aluminum alloy Ce containing 0%, 0.39% and 0.81% Ce, grains were the smallest, second phase or inclusion was the least and evenly distributed, and matrix structure of the alloy was improved when Ce content was 0.39%. Compared to the Re-free 7A04, corrosion weight loss of the 7A04 aluminum alloy containing Ce was significantly lower, and resistance of the rust layer increased, and the alloy containing 0.39% of Ce exhibited the highest resistance of rust layer. Three kinds of 7A04 aluminum alloy are all subject to obvious local corrosion, mainly the pitting. The addition of rare earth Ce changes phase T and S in non-rare earth aluminum alloy, produces new fine massive intermetallic compounds, refines uniformity of structure, increases the resistance of corrosion rust layer, enhances protective capability of the rust layer against substrate and improves marine atmospheric corrosion resistance. Among three kinds of 7A04 aluminum alloy, the one containing 0.39% Ce exhibits the best corrosion resistance.